Diluting system and method

ABSTRACT

A system and a method for automatically, accurately diluting chemical solutions on an industrial scale based upon real time weight measurements of chemical and diluent weight is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This invention claims priority under 35 U.S.C. §119 to U.S.Provisional Application No. 60/316,580, entitled DILUTING SYSTEM ANDMETHOD and filed Aug. 31, 2001, the entire content of which is herebyincorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates to a system for preparing diluted chemicalsolutions for use in industrial processes. More particularly, it relatesto an apparatus and associated controller for preparing and dispensingsuch solutions and the methods of diluting which they permit.

BACKGROUND OF THE INVENTION

[0003] Traditionally, diluting chemicals from their neat chemicalstrengths to something less has been accomplished via a venturi methodor by volume via a level probe in a dilution tank. Both of these methodshave drawbacks which cannot be solved due to inherent limitations intheir technologies.

[0004] In the case of a typical venturi dilution method, a flow ofdiluent is passed through a venturi. This flow creates a suction intowhich predilution material is drawn from a feed tank. The two flows mixin the venturi to form the desired diluted stream. This method is veryinaccurate. It is adversely affected by variables in the diluentvelocity, by any changes in flow cross-section, such as those whichoccur if there is even the slightest fouling or contamination of theventuri, and by any changes in back pressure in the undiluted chemicalfeed tank.

[0005] The level probe method bases the dilution on a series of volumesmeasured in a dilution tank. Conventionally, in the case of dilution,this involves measuring a predetermined volume of predilution materialinto the dilution tank and thereafter adding a similarly predeterminedvolume of diluent to the tank and mixing. (Of course, the order ofaddition can be reversed, if desired.) This process has thedisadvantages of not permitting user flexibility in changing thestarting or ending solution strengths. In addition, to get an accuratesolution strength in weight percent using level probes, the operatormaking the dilution must manually account for differences in thespecific gravity of the predilution material and the diluent.

[0006] One setting where dilutions are commonly carried out is in thefield of water treatment. In water treatment facilities it is becomingless desirable to store and add gaseous chlorine to water as a sterilantand purification aid. Government regulators are increasingly concernedabout environmental and health hazards which can arise when gaseouschlorine is inadvertently released. Sodium hypochlorite is an attractivealternative. This compound is sold commercially as aqueous solutions. Tominimize transportation and storage costs, these aqueous solutions areas concentrated as possible. Commonly these concentrated feeds containabout 10-16% by weight sodium hypochlorite. When this material is used,it is often at a substantially lower concentration which is achieved bydilution of the commercial feed solution. This dilution is carried outon an as-needed basis around the clock in most water treatmentfacilities.

[0007] In the case of sodium hypochlorite, this dilution is notstraightforward. The chemical make up of the feed solution varies withtime because the hypochlorite exists in solution in equilibrium withhypochlorous acid which in turn is capable of disproportionating togenerate free chlorine which can escape as a gas. Thus, theconcentration of a supply of hypochlorite will be decreasing with timeand the specific gravity of the supply solution will be decreasing aswell as the chlorine is given off. Also, the need for correct treatmentof water is a matter of public health so there is a strong desire for adilution system and method which can operate reliably, document accurateoperation and minimize the chances for operator error.

BRIEF DESCRIPTION OF THE INVENTION

[0008] We have now discovered that solutions of chemicals such as sodiumhypochlorite can be diluted most accurately and reliably with a highdegree of automation in common industrial settings when the dilution isbased upon the actual weights of chemical and diluent employed. The useof weight values facilitates corrections and adjustments based uponchanges in neat chemical and/or diluent composition. They alsofacilitate corrections based upon detection of overshoots in the feed ofeither material.

[0009] Thus, in one aspect this invention provides a substantiallyautomated dilution control system for diluting a liquid solution orsuspension of a chemical such as sodium hypochlorite. This systemincludes a dilution tank of known capacity for preparing the chemical ina desired diluted concentration. This tank is mounted upon an electronicscale which is capable of generating an infinite series of weightsignals related to the weight of the tank when empty and when partiallyor completely filled. The tank is in liquid communication with a sourceof concentrated or “neat” chemical and a source of diluent. Theconcentrated chemical is of a variable, but known or determinable,concentration. The flows of chemical and diluent are controlled by adiluent flow controller and a chemical flow controller, respectively,both of which are, in turn controlled by a microprocessor-based basedsystem controller. The weight signals from the scale are transmitted tothe system controller. The system controller is capable of receiving thefollowing pieces of data:

[0010] (1) a value related to the dilution tank capacity;

[0011] (2) a value related to the variable, concentrated chemicalconcentration;

[0012] (3) a value related to the desired diluted concentration; and

[0013] (4) a series of weight signals from the scale.

[0014] The controller calculates the weights of concentrated chemicaland diluent required to provide a target weight of diluted chemical ofdesired diluted concentration which does not exceed the known capacityof the dilution tank. The system controller controls the chemical feedflow controller and the diluent feed flow controller based upon theseries of weight signals received from the scale to produce a producedweight of diluted chemical of the desired diluted concentration. Theproduced weight corresponds closely to the target weight of dilutedchemical. The value related to the variable chemical concentration maybe a concentrated value calculated on the basis of other decompositionrate constant, temperature and time, it may be a value based on directchemical analysis of the concentrated chemical or it may be a valuebased upon measurement of specific gravity of the concentrated chemicalor the like.

[0015] In another aspect, this invention provides a method for dilutinga liquid solution or suspension of a chemical to a desired dilution.This method involves obtaining a dilution system as described just aboveand operating the system in one of two manners. The first mannerinvolves the steps of:

[0016] (a) inputting into the system controller information concerningthe target amount of diluted chemical and/or the capacity of thesystem's dilution tank, the concentration of the concentrated chemicalfeed and the desired dilution;

[0017] (b) calculating in the system controller the amount ofconcentrated chemical feed having a known, but variable, concentratedchemical concentration required to produce the target weight of dilutedchemical not exceeding the capacity of the dilution tank;

[0018] (c) charging concentrated chemical feed to the dilution tank;

[0019] (d) transmitting to the system controller a weight signal relatedto the weight of concentrated chemical feed measured by the system'sscale as actually charged to the tank;

[0020] (e) controlling the flow of concentrated chemical into thedilution tank with the system controller and the concentrated chemicalflow controller so that the actual weight of concentrated chemicalcharged does not exceed the weight required to produce the target weightof diluted chemical and the capacity of the dilution tank;

[0021] (f) calculating in the system controller the amount of diluentrequired to produce the target weight of diluted chemical not exceedingthe capacity of the dilution tank;

[0022] (g) charging diluent to the dilution tank;

[0023] (h) transmitting to the system controller a weight signal relatedto the weight of diluent measured by the system's scale as actuallycharged to the tank; and

[0024] (i) controlling the flow of diluent with the system controllerand the diluent flow controller so that the actual weight of diluentcharged does not exceed the weight required to produce the target weightof diluted chemical and the capacity of the dilution tank.

[0025] The second manner of operation is similar but is generally lesspreferred and involves adding a measured weight of diluent to the tankand thereafter adding a measured weight of concentrated chemical in theamount calculated by the system controller as needed to obtain thedesired dilution and target volume.

[0026] In a further aspect, this invention provides a monitoring systemfor a liquid concentrated chemical and expressing the chemicalconcentration in “equivalent pounds of chlorine”. This system includes atank of known capacity. The tank is mounted upon an electronic scalewhich is capable of generating a series of weight signals related to theweight of the tank when empty and at various levels of filling. Aplurality of level sensors are located inside the tank which are capableof generating a series of level signals related to the level of the tankat various levels of filing. The tank is in liquid communication with asource of liquid concentrated chemical having a first, but variable,concentrated chemical concentration. The system controller is capable ofreceiving the following pieces of data:

[0027] (a) a value related to the tank capacity;

[0028] (b) a value related to the level of the concentrated chemical inthe tank;

[0029] (c) a value related to the variable, concentrated chemicalconcentration; and

[0030] (d) a series of weight signals from the scale.

[0031] The controller calculates the weight of concentrated chemicalconcentration, and converts the weight of concentrated chemicalconcentration into an equivalent weight.

[0032] It will be understood by those skilled in the art of chemicaldilution that either of these processes can be operated with themajority or all of the concentrated chemical feed or the diluent addedin one unit or alternatively the materials can be added in severalportions of the whole if this would facilitate mixing, or offer otheradvantages. In either case, the system will calculate the amounts ofmaterials needed and provide the desired dilution and final targetvolume.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] This invention will be further described with reference beingmade to the accompanying drawings in which:

[0034]FIG. 1 is a cross-section elevation view of a dilution system ofthis invention.

[0035]FIG. 2 is a schematic view of the component layout of thecontroller used in the system and method of the present invention.

[0036]FIG. 3 is a schematic view of the controller face illustrating thekeypad functions and displays of the controller used in the system andmethod of this invention.

[0037] FIGS. 4(A, B and C) is a cross-section elevation view of threeversions of an optional portion of the dilution system which is capableof providing values related to the concentration of the concentratedchemical feeding.

[0038]FIG. 5 is three series of cross-section elevation views of aportion of dilution system of FIG. 4 which depict, in story board form,the operation of the three versions of the optional portion of thesystem which provides values related concentration of the concentratedchemical feeds.

[0039]FIG. 6 corresponds to FIG. 4 and shows a third embodiment of theoptional portion of the system for determining a value related to theconcentrated feed concentration.

[0040]FIG. 7 corresponds to FIG. 5 showing the operation of this thirdembodiment.

[0041]FIG. 8 is a cross-section elevation view of an alternativeembodiment of a dilution system of this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0042] Turning to the drawings, a system 100 for diluting chemicals inaccord with this invention is shown in FIG. 1. This system and themethod of its use will be described in the context of a sodiumhypochlorite concentrate solution as the concentrated chemical and wateras the diluent. It will be appreciated that these materials are notlimiting and that this system and its use could work with a wide rangeof chemicals and diluents.

[0043] System 100 includes dilution tank 10. The capacity of this tank10 is known and most commonly is smaller than might typically beselected in a manually-operated setting. This use of asmaller-than-usual dilution tank 10 is advantageous. It permits morefrequent adjustments in diluted product concentration as may be neededto deal with changing needs for the diluted chemical. It also allows fora smaller capital investment. Tank 10 is positioned upon scale 12 whichcan generate signals related to the empty weight, full weight andpartially full weight of the dilution tank. Although not critical to theinvention, tank 10 and scale 12 are shown in FIG. 1 positioned on anelevated platform for gravity feed to a working tank 35. Concentratedchemical solution or suspension 17 (also known as neat chemical) isstored in chemical supply tank 16.

[0044] Chemical solution/suspension 17 can be transferred through line18 to tank 10. Line 18 includes a flow control device, in this caseembodied as controllable pump 20, which controls the flow of chemical totank 10. As chemical 17 is added to the tank 10, scale 12 generatessignals to indicate the exact weight of concentrated chemical solutioncharged to tank 10. A diluent 25 is provided to tank 10 by line 22. Theflow of diluent 25 is also controlled by a flow control device, in thiscase solenoid valve 24. When valve 24 is opened, diluent 25 enters tank10. Scale 12 detects and signals the weight of diluent 25 added to tank10. The signals from scale 12 are transmitted to a system controller 26via line 28. System controller 26 transmits control signals to pump 20and valve 24 via lines 30 and 32 respectively. As batches of dilutedchemical 33 are produced, they are taken off for use or storage inworking tank 35 via line 34 and dump valve 36. Valve 36 can be a manualvalve but preferably is also controlled by system controller 26 via line52.

[0045] Controller 26 and its several functions are described in moredetail with reference to FIGS. 2 and 3. As shown there, line 28 inputsweight data from scale 12 and lines 30, 32 and 52 send control signalsto pump 20, valve 24 and dump valve 36, respectively. Controller 26includes microprocessor CPU 40, memories 42 and 44, display 46, inputkeyboard 48 and relays 50. These relays, A, B, C and D, can control thevalves or pumps for neat chemical supply, water supply and dump valve,for example. They also can actuate alarm 76 if a warning is called for.

[0046] Controller 26 also includes a power supply 78 and scale signalinput 80 which receives signals from line 28 and a series of signaloutputs 82 for providing signals which can be displayed to indicate (a)that the controller is active; (b) the weight of dilute productremaining; and (c) the weight of concentrate remaining. There arerepresentative output signals, others can be provided as determined bythe user.

[0047] As shown in FIG. 3, the controller 26 includes a display 46. Thetype of information displayed is commonly set by the controller or bythe operator activating input keyboard 48. For example, this keyboard 48can include a numeric keypad 84 which the operator can use to input datainto the controller. Controller 26 can include reset button 86 which canbe used if an error is made during data input. It can also include aseries of function keys such as shown as A-J. This can cause operationsto be carried out or information such as the following to be displayed:“A” Feed Rate Toggles through a multi-function display: Dilute Rate;Pure Rate “B” Daily Used Toggles through Dilute Values: Dilute Used;Pure Used “C” Total Used Toggles through a multi-function display: DateLast Cleared; Total Neat; Total Water; Total Dilute; Total Pure; ClearTotals “D” Batch Review Toggles through a multi-function display: NeatStrength; Dilute Strength; Batch Size; Neat Target; Water Target “E”Start Starts Dilution Process “F” Enter Data Entry, Accept or Menufunction access “G” Del Backspace, Delete or Escape “H” Menu OperationsFunction Menu Description Alarm Log Review time and date for alarm andevents Manual Allows manual Operation operation of neat/water/dump BatchSetup Input batch process parameters Set Alarm Input alarm values ValuesSet Scale Zero the Scale Zero Time & Date Current Time and Date ClearTotals Clear Totals/Reset Zero Review Batch Review batch processparameters “I” Refill Chem (Optional) Keep track of Neat ChemicalSupply: Refill/Change Out Neat; Neat Amount (lbs.); Neat Strength (%);Dilute Strength (%) “J” Stop Stop the Dilution Process

[0048] This information and these functions give the operator control ofthe dilution process and the data related to it.

[0049] Controller 26 is programmed to accept input values related to:

[0050] (a) the concentration of the concentrated chemical;

[0051] (b) the desired dilution; and

[0052] (c) the batch size not to exceed the capacity of tank 10.

[0053] The system controller 26 takes that information and calculatesthe amounts of concentrate 17 and diluent 25 required. The systemcontroller 26 also controls the flow control devices to admit theseamounts. Using the data supplied by the scale, it notes the actualweights of concentrate and diluent used and can make adjustments toachieve the desired dilution.

[0054] The input value relating to the concentration of the concentratedchemical can be a specific concentration value used directly by thesystem controller 26 in calculating the amount of concentrated chemicalto be used. It can be one or more concentration-related values fromwhich the system controller 26 can calculate the concentration of theconcentrate or neat material. This latter case can be illustrated withreference to a concentrated solution of sodium hypochlorite.

[0055] As noted, this material undergoes degradation over time. In thiscase the values inputted could be an initial concentration value, avalue related to the length of time since the initial concentration wasdetermined and a temperature value (if temperature was a variable duringthe period since the initial concentration was determined). The systemcontroller 26 can be programmed to calculate a concentrated chemicalconcentration based upon these values and a degradation rate constant.Similar calculation techniques can be used with other chemicalconcentrates.

[0056] In the case of solutions chemicals which undergo a weight changeas their concentrations change, the system with its ability to quantifymaterials by weight can be configured to provide a measurement valuewhich is directly related to concentration. Three examples of this areshown in FIG. 4.

[0057] As noted above, when sodium hypochlorite degrades, it gives offchlorine, a heavy material, as a gas. The remaining partially degradedhypochlorite solution, has a lower specific gravity as a result of theloss of chlorine with the exact specific gravity being directly relatedto the actual concentration of sodium hypochlorite in the solution.

[0058] Since the system is already equipped with scale 12 to measure theweight of materials added to dilution tank 10, if the volume of such anaddition is known, its specific gravity and hence concentration can becalculated from weight values provided by scale 12.

[0059]FIG. 4A shows one system 104 capable of providing the informationabout specific gravity. This system 104 has all the elements of system100 of FIG. 1 and is shown in operation in the manner described withreference to FIG. 1 and system 100. System 104 includes a chamber 54 vialine 56. This flow is controlled by valve 58 which is in turn controlledby controller 26 (which is not shown in this Fig.). When concentratechemical solution 17 is being fed to chamber 54, its flow via line 18 totank 10 can be independently controlled by valve 60. Chamber 54 isequipped with an overflow line 62 and delivery line 64. The flow offluid out of chamber 54 via line 64 is controlled by valve 66.

[0060] As depicted quite clearly in FIG. 4B, when feed is being fed tochamber 54, valve 66 is closed, and excess concentrate is retrieving tosupply tank 16 via line 62, a volume “V” of concentrate 17 is containedwithin chamber 54. V is a constant which can be measured as the systemis being constructed or installed. If chamber 54 is filled as shown inFIG. 4B such that volume “V” is attained, the flow of concentrate 17into 54 via line 18 is halted and the volume V is then added to tank 10,there will be a weight change to tank 10 which can be accuratelydetermined by scale 12. This weight value, combined with the volumevalue V can be used to determine a specific gravity for the concentrate17 which is directly related to the concentration of the chemicalconcentrate. This can be done in controller 26. Since the volume V isconstant, the weight change value alone when the volume V is added canbe used by controller 26 as a value related to concentration.

[0061] This same process for determining concentration can be carriedout in system 106 shown in FIG. 4B. This system is simplified in that itdoes not have a separate line for adding additional concentratedchemical after the volume V is added but rather passes the additionalvolume through chamber 54 and open valve 66.

[0062]FIG. 4C shows an alternative embodiment of the systems of FIGS. 4Aand 4B. The system 108 of FIG. 4C has all the elements of the systems104, 106 of FIGS. 4A and 4B, and is shown in operation in the mannerdescribed with reference to FIG. 1 and system 100. However, in thesystem 108 as shown in FIG. 4C, rather than running the overflow lines62 and delivery line 64 to the supply tank 16, the overflow line 62 anddelivery line 64 runs from the chamber 54 to the dilution tank 10.

[0063] In operation, a chemical accumulator in the system controller 26is “zeroed” so that the amount of concentrate 17 that is added to thedilution tank 10 can be calculated. The chemical concentrate 17 is thenfed to the chamber 54 via line 18. When the chamber 54 begins tooverflow, the excess chemical concentrate 17 is fed into to the dilutiontank 10 via overflow line 62. As a result of the addition of chemicalconcentrate to the dilution tank 10, the scale 12 detects an increase inweight and sends a signal to the system controller 26 to shut off thecontrollable pump 20.

[0064] The chemical accumulator in the system controller 26 memorizesthe weight of “overflow chemical concentrate” for later recall.

[0065] The system controller 26 starts the chemical concentrationanalysis process by adding volume V from the chamber 64 to the dilutiontank 10 via line 64 and valve 66. Volume V is then weighed by the scale12 to determine the strength of chemical concentrate 17 via specificgravity by the system controller 26. When the specific gravity of volumeV is determined and a chemical concentrate target is established, thepump 20 is activated to add the chemical concentrate 17 via the line 18,the chamber 54, the line 64 and the valve 66. The weight of volume V andoverflow chemical concentrate previously added to tank 10 is alsoapplied towards chemical concentrate target value.

[0066] The use of a volume “V” as a means of determining concentrationcan be further exemplified by the several sequential views shown in FIG.5. In FIG. 5 the “A” series of views is based on the system shown inFIG. 4A, the “B” series corresponds to the system in FIG. 4B and the “C”series corresponds to the system in FIG. 4C.

[0067] In FIGS. 5A¹, 5B¹ and 5C¹ the system is shown with tank 10 empty,although in actual practice it can contain diluted chemical as long asits weight is known prior to the time the volume V of concentrate isadded to it. As shown in FIGS. 5A², 5B² and 5C² in the second stageconcentrated chemical solution is pumped to chamber 54 via line 18.Valve 66 is closed and concentrate is fed until it flows out of vessel54 and is returned to tank 16 via line 62 in FIGS. 5A^(2 and 5B) ². InFIG. 5C², the concentrate is fed until it flows out of vessel 54 andinto tank 10 via line 62. The volume between valve 66 and the overflowport leading to line 62 has previously been measured as volume V.

[0068]FIGS. 5A³, 5B³ and 5C³ show this amount of concentrate is added totank 10 via line 64. Scale 12 determines the weight change of tank 10when volume V of concentrate is added to it.

[0069] This value is used by controller 26 to calculate the amount ofconcentrate needed to complete a batch of diluted chemical and thisamount is then added as shown in FIGS. 5A⁴, 5B⁴ and 5C⁴ by controllingpump 20 and valves 60 or 66 for concentrate. An amount of diluent 25 iscalculated and added via line 22 and valve 24. As always, the weights ofmaterials actually added are measured by scale 12 and this informationis used by controller 26 in controlling the operation of pump 20 andvalve 24.

[0070] One can also determine the weight of a known volume ofconcentrate using a known portion of the volume of tank 10 as themeasured volume, so long as tank 10 is consistently emptied before theconcentrate is added.

[0071]FIG. 6 shows one configuration for doing this. A return line 70with valve 72 is placed between dilution tank 10 and supply tank 16.This line is positioned in tank 10 so that it defines a known volume Vof concentrate in the tank 10 when the tank if filled to its level.

[0072] As shown in FIG. 7A, initially tank 10 is empty. In FIG. 7B flowcontroller 20 is feeding concentrate through line 18 to tank 10. Valve36 is closed and tank 10 is filled to a known volume V defined by line70 and valve 72. As shown in FIG. 7B, excess concentrate is passedthrough line 70 back to tank 16.

[0073] As shown in FIG. 7C, controllable pump 20 is then shut off andthe flow of excess concentrate through line 70 is completed. Now thevolume of concentrate in tank 10 is exactly the volume “V” defined bythe location of line 70 leaving tank 10. The weight of this volume V isdetermined by scale 12 and this value is used by controller 26 to definethe concentration of the concentrate. The controller then calculates theamount of concentrate and the amount of diluent required closes valve 72and meters these amounts of concentrate and diluent into tank 10 asshown in FIG. 7D to complete the batch of diluted chemical.

[0074] As noted in FIG. 3, the controller can be programmed to perform awide range of additional functions and achieve a wide range ofadditional advantages.

[0075] The dilution system of this invention provides many advantagesover the dilution systems and methods of the past. For one, it permitsthe operator to directly “dial a solution strength” into the controllerthrough input pad 48 and achieve this desired dilution with little or nomanual intervention.

[0076] In addition, and importantly, the automation and weight-basedaccuracy provided by the present system allows batches to be made morefrequently, (and thus to be smaller.) With this “MB squared” (MassBased+Micro Batch) technology, the user can instantly adjust todifferent beginning and ending solution strengths in order to maximizedosing accuracy and consistency. This system and method for continuouslyand automatically creating small weight-based batches can achieveaccuracies of 1 part in 1000 of desired solution strength.

[0077] Following is a further summary of the main features and benefitsthat this dilution control system can provide:

[0078] Flexibility

[0079] Dial-A-Solution Strength: The dilution controller allows the userto easily enter or change a beginning (neat) solution strength, and theneasily enter or change the desired ending solution strength (dilute)based on the needs of the application. The controller then automaticallycalculates the necessary amounts of water and the chemical needed tomake a predetermined batch size and batch strength. For chemicals likesodium hypochlorite, this flexibility is extremely important because thebeginning (neat) strength is continually decreasing and the endingsolution strength needed will change as water demand changes. Thisflexibility offers the following benefits:

[0080] (a) it allows metering pumps which feed hypochlorite to watersystems to run at optimum efficiency by allowing the changing of the endsolution strength based on the water demand;

[0081] (b) this gives greater range to the low end of such meteringpump, delivers a more repeatable and accurate chemical dose, optimizescompound loop controls because of a more consistent/accurate chemicaldose, makes it easy to adjust to changing or different neat chemicalstrengths and makes it easy to adjust to changing water capacities orwater demands; and

[0082] (c) the accuracy and repeatability achieved using this system isoutstanding. By using mass based batching combined with making multiple“micro batches”, the controller can achieve the most accurate form ofdilution control available. This process can be continuous and automaticwhen in the “System Activated” mode. This eliminates under and overdosing and achieves desired solution strengths as accurate as 1 part in1000.

[0083] Chemical Accountancy:

[0084] The controller can also provide chemical accountancy functions.The dilution controller has a number of features that allow the user totrack: Remaining Chemical Quantity, Chemical Feed Rates and ChemicalUsages. By tracking these various figures, the user can gain superiorcontrol of their chemical dosing system in order to save money onchemicals, satisfy government reporting requirements and keep theirwater and treatment plant safe. Features include displays of UsageTotalizer for Neat chemical, Dilute Chemical, Pure Chemical and Water.While measured in weight, these values can be expressed in weight orvolume units as desired. The controller also has a Daily UsageDatalogger which stores each of the previous ten days usage of dilutechemical. The Datalogger can also convert daily dilute chemical usage to“pure” chemical usage, if desired. “Pure” is defined as 100%concentration of reactant.

[0085] The controller can also provide additional reports such as NetRemaining Dilute chemical present in the dilution tank and Feed Rate forDilute chemical (also converts to current “pure” chemical feed rate).

[0086] Alarms:

[0087] The controller can also be set to activate process alarms. Bymonitoring the weight of the dilution tank in real time eithercontinuously or at predetermined time intervals, and comparing theweights measured with inputted or calculated desired values, thecontroller can pick up potential problems with the chemical dosingsystem that would otherwise go undetected. This prevents the possibilityof over- or underdosing the water supply. Alarms can pause the dilutionprocess and give a 0.5 amp dry relay contact which can be used totrigger a variety of alarms.

[0088] These alarm functions can include:

[0089] 1. Slow neat chemical transfer alarm: This alarm would betriggered if the system controller noted that the weight of neatchemical charged to the dilution tank, as measured by the scale, wasless than expected. This prevents underdosing by indicating that theneat chemical feed vessel chemical is empty, a transfer pump failure orblockage in the neat transfer lines.

[0090] 2. Slow diluent transfer alarm: This alarm would be triggered ifthe system controller noted that the weight of diluent charged to thedilution tank, as measured by the scale, was less than expected. Thisprevents overdosing by indicating a problem with the diluent supplypressure or a solenoid valve failure.

[0091] 3. Slow dilute chemical feed alarm: This alarm would be triggeredif the system controller noted that the weight of diluted chemical inthe dilution tank, as measured by the scale, was greater than expected.This prevents underdosing by indicating a metering pump failure and/or ablockage in the out feed lines.

[0092] 4. Maximum chemical usage alarm: This alarm would be triggered ifthe system controller noted that the weight of diluted chemical in thedilution tank, as measured by the scale, was less than expected. Thisprevents prolonged overdosing by giving an alarm that the desiredmaximum usage rate of chemical has been or is being exceeded.

[0093] 5. Dilution tank high level alarm: This alarm would be triggeredif the system controller noted that the weight of material in thedilution tank, as measured by the scale, was equal to or exceeded thecapacity of the dilution tank and the desired degree of dilution had notbeen achieved. This could occur if there had been an incomplete transferof the preceding batch. This alarm prevents overfilling of the dilutiontank.

[0094] 6. Batch strength not available alarm: This alarm is triggeredwhen the controller notes a weight of chemical or diluent and a targetdilution value which would lead to overfilling the dilution tank. Thisalarm prevents overfilling of the dilution tank.

[0095] Vent Lines, Check Valves and Flow Switches

[0096] The dilution systems can also be designed with additional safetyfeatures to prevent potential chemical spills. Chemical spills can beavoided by adding vent lines, check valves and flow switches to any ofthe tanks so that the chemical concentrate is contained within thetanks. These safety features function as follows:

[0097] Shown in FIG. 4C is the integration of vent lines 110, 116 fromboth the dilution tank 10 and the working tank 35 to prevent the tanksfrom vacuum locking as a result of a decrease in the tank levels of thediluted chemical or end solution 33. The vent lines 110, 116 willpreferably vent to the atmosphere, however, it can be appreciated thatthe vent lines 110, 116 can vent to a waste tank or other disposalsystem. Furthermore, as a safety precaution, a check valve 114, 120 canbe added at the top of the vent lines 110, 116 which will prevent anyinadvertent overfilling of either the dilution tank 10 or working tank35. A flow switch 112, 118 located in the vent line 110, 116 fordetecting flow in the vent lines 110, 116 can also be provided to shutdown the entire dilution process via a main relay breaker if either thedilution tank 10 or working tank 35 is overfilled.

[0098] Other features and benefits include a straightforward proof ofaccuracy by simply placing a known weight on the weighing platform.There is also easy checking of batch parameters: the controller canprovide a review function to review dilution batch parameters. It canalso allow the operator to “abort” or “continue” a batch if it isterminated in the middle of a “Fill” It can also allow the operator toeither “manually” finish a batch or “dump” it to the feed tank if apartial batch exists in the dilution tank. The controller can also beset up to provide an “auto compensation” function that automaticallyrecalculates diluent target when the calculated requirements ofconcentrated chemical is exceeded.

[0099] In addition to the benefits that the dilution control system canprovide as set forth above, the system controller 26 can provide manyadditional automation and weight-based features for improved accuracy ofchemical concentrate and end solution delivery to a water system. Thesystem controller 26 can provide automatic adjusting of end solutionstrength based on water demand, equivalent pounds of chlorine gasreadings for easier reading of available chemical concentrate, andautomatic refilling of the working tank based on water demand.

[0100] Automatic Adjusting of the End Solution Strength

[0101] The system controller 26 includes the ability to automaticallyadjust the diluted chemical strength or end solution strength based onwater demand. The ability to automatically adjust the diluted chemicalstrength or end solution provides the user with the ability optimizepump speeds and residual loop controls. In addition, by automatingstrength of the end solution based on water demand, the system allowsbatches to be made more frequently, and thus smaller without affectingthe accuracy and consistency of the end solution.

[0102] In one embodiment, as shown in FIG. 1, a metering pump 130 feedsdiluted chemical or end solution 33 to a water system 140. As with anymechanical pump, the metering pump 130 has an optimum efficiency rangewherein the pump operates while pumping end solution 33 to the watersystem. Thus, if the amount of end solution 33 needed in the watersystem 140 is reduced, the amount of end solution 33 delivered via themetering pump 130 will be adjusted by reducing the speed of the meteringpump 130. Alternatively, if the water demand increases, the speed of thepump will be increased to deliver more end solution 33 to the watersystem 140. However, if the pump speed decreases or increases outside ofits optimum efficiency range, the accuracy or delivery of a repeatableand accurate chemical dose by the metering pump 130 is compromised.Accordingly, it would be desirable that the metering pump 130 operate atall times in its optimum efficiency range.

[0103] In order to overcome these problems, the system controller 26 hasthe capability of automatically adjusting the volume and strength of theend solution 33. In operation, the system controller 26 receives inputsignals 132, 142 from the metering pump 130 and water system 140,respectively, as to the pump speed and the amount of water in the watersystem. If the pump speed is within the optimum efficiency range, thesystem controller 26 will not adjust the end solution 33 strength.However, if the amount of water in the water system 140 has decreased,which results in the pump speed also decreasing beyond a desired pumpspeed, the system controller 26 automatically adjusts the strength ofthe end solution 33.

[0104] Generally, a metering pump's 130 optimum efficiency isapproximately 50 to 70 percent of its maximum speed. For example, at itsoptimum efficiency, a metering pump 130 will pump a volume of 100gallons per minute of 6 percent chlorine end solution which is capableof treating 500 gallons per minute of water in a water system 140.However, if the volume of the water in the system decreases to 250gallons per minute, the amount of end solution 33 required to treat thewater will be approximately one-half of the original amount orapproximately 50 gallons per minute of 6 percent chlorine solution.Alternatively, the amount of end solution could be adjusted to 100gallons per minute of 3 percent chlorine solution which would providethe same effective treatment to the water system 140. Thus, by adjustingthe end solution strength, the metering pump 130 will continue tooperate at its optimum efficiency of 50-70 percent of its capacity bypumping 100 gallons per minute.

[0105] In order to accomplish an automated adjustment of the endsolution, strength, a plurality of signals 132, 142 are sent from themetering pump 130 to the system controller 26. The system controller 26will receive the signals 132, 142 indicating the metering pump 130 speedin strokes per minute, which in turn can be used to calculate theefficiency rate of the pump, and the amount of water in the water system140, respectively. If the signals 132, 142 indicate that the flow ofwater in the water system 140 has decreased or is decreasing, which inturn would result in a decrease in the pump speed outside of themetering pump's 130 optimum efficiency range, the system controller 26calculates a reduced end solution strength by decreasing the amount ofdiluent 25 being added to the chemical solution 17. Once the endsolution strength is decreased, it will be delivered to the working tank35 and pumped through the metering pump 130 into the water system 140.

[0106] The system controller 26 is also able to increase the endsolution 33 strength in the event that the amount of water in the watersystem 140 increases. Specifically, if the signal 142 from the watersystem 140 indicates an increase in the amount of water in the watersystem 140, which results in the metering pump 130 having to operate ata higher efficiency than desired, the amount of diluent 25 can beincreased in the volume of diluted chemical or end solution 33 deliveredto the water system 140. Thus, by increasing the end solution strength,the metering pump 130 will not be required to pump as much end solution,such that the metering pump 130 speed remains within its optimumefficiency range. It can be also appreciated that the system controller26 can be programmed to automatically change the end solution strengthbased solely on water demand in the water system or any other variablewithin the system wherein a change in the end solution strength isdesired.

[0107] Equivalent Pounds of Chlorine Gas Monitor:

[0108] Generally, concentrated chemicals, such as sodium hypochlorite,vary in strength and are measured or given in a “volume and samplestrength” which is described as 100 gallons of 12 percent sodiumhypochlorite. However, it would be desirable to provide the amount ofremaining chemical concentrate or sodium hypochlorite in a given systemin “equivalent pounds of pure chlorine gas”.

[0109]FIG. 8 shows a system 150 capable of providing “equivalent poundsof chlorine pure gas”. This system 150 includes a system controller 26which provides continuous monitoring of the volume and weight of sodiumhypochlorite in a given tank. For purposes of an example, the system 150will be described in relationship to the feed tank 16; however, the samesystem would also work in a working tank or any other type of tankcombining a source of liquid concentrated chemical having a first, butvariable, concentrated chemical concentration. The feed tank 16 ispositioned upon a scale 160, similar to scale 12, which can generatesignals 162 related to the empty weight, full weight and partially fullweight of the feed tank 16. Typically, the feed tank 16 will store orhold a concentrate chemical solution or suspension 17, such as sodiumhypochlorite. In addition, the feed tank 16 will have a plurality oflevel sensors 164 for measuring and generating a signal 166 as to thevolume of the chemical solution 17 within the feed tank 16.

[0110] In one embodiment, the weight and volume of the chemical solution17 are continuously monitored and sent via a plurality of signals 162,166 to the system controller 26. The system controller 26 calculates thespecific gravity and thus the strength of the chemical in the feed tank16 based on the weight and volume of the chemical concentrate. Thequantity of the chemical concentrate will be measured in equivalentpounds of pure chemical concentrate by multiplying the strength of thechemical concentrate times the weight of chemical concentrate to producea reading in equivalent pounds of pure chemical. The monitoring processis continuous such that an end-user can determine the amount ofavailable chemical concentrate in equivalent pounds rather than a samplestrength. The available chemical concentrate in equivalent weight isshown on the display 46 of the system controller 26, so that an operatorcan visually view the equivalent weight at any moment in time. It can beappreciated that the equivalent weight can be in pounds, tons, grams,kilograms or any other unit of weight.

[0111] While this invention has been described with reference to thepreferred embodiment described above, it will be appreciated that theconfiguration of this invention can be varied and that the scope of thisinvention is defined by the following claims.

What is claimed is:
 1. A dilution system for a chemical comprising: adilution tank of known capacity for preparing the chemical in a desireddiluted concentration, the tank mounted upon an electronic scale, thescale being capable of generating a series of weight signals related tothe weight of the tank when empty and at various levels of filling; asource of liquid concentrated chemical feed having a first, butvariable, concentrated chemical concentration; a chemical feed flowcontroller for controlling the flow of concentrated chemical feed to thedilution tank; a source of liquid diluent; a diluent flow controller forcontrolling the flow of diluent to the dilution tank; and a systemcontroller: for receiving: (a) a value related to the dilution tankcapacity; (b) a value related to the variable, concentrated chemicalconcentration; (c) a value related to the desired diluted concentration;and (d) a series of weight signals from the scale; for calculating theamounts of concentrated chemical and diluent required to provide atarget amount of diluted chemical of desired diluted concentration whichdoes not exceed the known capacity of the dilution tank; and forcontrolling the chemical feed flow controller and the diluent flowcontroller based upon the series of weight signals to produce a producedquantity of diluted chemical, the produced quantity related to thetarget amount of diluted chemical and not exceeding the capacity of thedilution tank.
 2. The dilution system of claim 1, additionallycomprising a working tank in liquid communication with the dilution tankand into which the diluted chemical can be passed.
 3. The dilutionsystem of claim 1, wherein the value related to the variableconcentrated chemical concentration is a concentrated chemicalconcentration.
 4. The dilution system of claim 1, wherein the chemicalundergoes degradation over time and the value related to the variableconcentrated chemical concentration is a value usable by the systemcontroller to calculate a concentrated chemical concentration value. 5.The dilution system of claim 1, additionally comprising a readablememory into which weight signals are stored said weight signals beingfrom the series of weight signals related to at least one of: the targetamount of diluted chemical produced by the dilution system; the weightof chemical present in the target amount of diluted chemical produced bythe dilution system; and the weight of diluent present in the targetamount of diluted chemical produced by the dilution system.
 6. Thedilution system of claim 5, additionally comprising a chamber of knownvolume in inlet liquid communication with the source of concentratedchemical feed and in outlet liquid communication with said dilution tankfor adding a known volume of concentrated chemical feed to the dilutiontank.
 7. The dilution system of claim 6, additionally comprising anoverflow line, said overflow line in outlet liquid communication withsaid chamber and inlet liquid communication with said source ofconcentrated chemical feed.
 8. The dilution system of claim 6,additionally comprising an overflow line, said overflow line in outletliquid communication with said chamber and inlet liquid communicationwith said source of dilution tank.
 9. The dilution system of claim 1,additionally comprising a slow neat chemical transfer alarm whichcompares a weight of concentrated chemical measured by the scale with aminimum weight value and triggers an alarm if the measured weight isless than the minimum value.
 10. The dilution system of claim 1,additionally comprising a slow diluent transfer alarm which compares aweight of diluent measured by the scale with a minimum weight value andtriggers an alarm if the measured weight is less than the minimum value.11. The dilution system of claim 1, additionally comprising a slowdilute chemical feed alarm which compares a weight of dilute chemicalmeasured by the scale with a maximum weight value and triggers an alarmif the measured weight is greater than the maximum value.
 12. Thedilution system of claim 1, additionally comprising a maximum chemicalusage alarm which compares a weight of dilute chemical measured by thescale with a minimum weight value and triggers an alarm if the measuredweight is less than the minimum value.
 13. The dilution system of claim1, additionally comprising a dilution tank high level alarm whichcompares the weight of material in the dilution tank, as measured by thescale with a maximum value related to the capacity of the dilution tankand triggers an alarm if the measured value is equal to or exceed themaximum value and the desired degree of dilution had not been achieved.14. The dilution system of claim 1, additionally comprising a batchstrength not available alarm which compares a measured weight ofchemical or diluent and based upon a target dilution value triggers analarm if dilution of the measured weight to the target dilution valuewill result in overfilling the dilution tank before the target dilutionis obtained.
 15. The dilution system of claim 1, additionallycomprising: (a) a slow neat chemical transfer alarm which compares aweight of concentrated chemical measured by the scale with a minimumweight value and triggers an alarm if the measured weight is less thanthe minimum value; (b) a slow diluent transfer alarm which compares aweight of diluent measured by the scale with a minimum weight value andtriggers an alarm if the measured weight is less than the minimum value;(c) a slow dilute chemical feed alarm which compares a weight of dilutechemical measured by the scale with a maximum weight value and triggersan alarm if the measured weight is greater than the maximum value; (d) amaximum chemical usage alarm which compares a weight of dilute chemicalmeasured by the scale with a minimum weight value and triggers an alarmif the measured weight is less than the minimum value; (e) a dilutiontank high level alarm which compares the weight of material in thedilution tank, as measured by the scale with a maximum value related tothe capacity of the dilution tank and triggers an alarm if the measuredvalue is equal to or exceed the maximum value and the desired degree ofdilution had not been achieved; and (f) a batch strength not availablealarm which compares a measured weight of chemical or diluent and basedupon a target dilution value triggers an alarm if the measured weightand the target dilution value will result in overfilling the dilutiontank before the target dilution is obtained.
 16. The dilution system ofclaim 1, additionally comprising at least one vent line in outlet liquidcommunication with said dilution tank.
 17. The dilution system of claim1, additionally comprising at least one vent line in outlet liquidcommunication with said working tank.
 18. The dilution system of claim16, additionally comprising a check valve and a flow switch wherein saidflow switch is able to shut down the system if flow is detected in saidvent lines.
 19. The dilution system of claim 17, additionally comprisinga check valve and a flow switch wherein said flow switch is able to shutdown the system if flow is detected in said vent lines.
 20. The dilutionsystem of claim 1, additionally comprising a pump for feeding dilutedchemical to a source of water wherein said system controller receives avalve related to a speed of said pump and calculates the amounts ofconcentrated chemical and diluent required to provide a target amount ofdiluted chemical of desired diluted concentration for operating saidpump at an optimum efficiency.
 21. The dilution system of claim 1,additionally comprising: a chemical supply tank of known capacity havinga source of liquid concentrated chemical feed, the chemical supply tankmounted upon a scale, the scale being capable of generating a series ofweight signals related to the weight of the tank when empty and atvarious levels of filing; a plurality of level sensors located insidethe chemical supply tank, the level sensors being capable of generatinga series of level signals related to the level of the tank at variouslevels of filing; and wherein the system controller calculates anddisplays an amount of concentrated chemical feed in a weight equivalent.22. A dilution control system for aqueous sodium hypochloritecomprising: a dilution tank of known capacity for preparing the sodiumhypochlorite in a desired diluted concentration, the tank mounted uponan electronic scale, the scale being capable of generating a series ofweight signals related to the weight of the tank when empty and atvarious levels of filling; a source of liquid concentrated sodiumhypochlorite feed having a first, but variable, concentrated sodiumhypochlorite concentration; a sodium hypochlorite feed flow controllerfor controlling the flow of concentrated sodium hypochlorite feed to thedilution tank; a source of water; a water flow controller forcontrolling the flow of water to the dilution tank; and a systemcontroller: for receiving: (a) a value related to the dilution tankcapacity; (b) a value related to the variable, concentrated sodiumhypochlorite concentration; (c) a value related to the desired dilutedsodium hypochlorite concentration; and (d) a series of weight signalsfrom the scale; for calculating the amounts of concentrated sodiumhypochlorite and water required to provide a target amount of dilutedsodium hypochlorite of desired diluted concentration which does notexceed the known capacity of the dilution tank; and for controlling thesodium hypochlorite feed flow controller and the water flow controllerbased upon the series of weight signals to produce a produced quantityof diluted sodium hypochlorite, the produced quantity related to thetarget amount of diluted sodium hypochlorite and not exceeding thecapacity of the dilution tank.
 23. In a system for preparing a dilutedchemical said chemical in concentrated form having a variableconcentration and a specific gravity which varies as a direct functionof the variable concentration, the improvement comprising thecombination of a tank for containing the diluted chemical, a scaledetermining the weight of material present in said tank and a chamber ofknown volume of supplying a measured known volume of concentratedchemical to said tank with the weight of said known volume determinableby the scale.
 24. A method for diluting a chemical to a desired dilutioncomprising the steps of: (a) obtaining a dilution control systemcomprising: a dilution tank of known capacity for preparing the chemicalin a desired diluted concentration, the tank mounted upon an electronicscale, the scale being capable of generating a series of weight signalsrelated to the weight of the tank when empty and at various levels offilling; a source of liquid concentrated chemical feed having a-first,but variable, concentrated chemical concentration; a chemical feed flowcontroller for controlling the flow of concentrated chemical feed to thedilution tank; a source of liquid diluent; a diluent flow controller forcontrolling the flow of diluent to the dilution tank; and a systemcontroller: for receiving: (i) a value related to the dilution tankcapacity; (ii) a value related to the variable, concentrated chemicalconcentration; (iii) a value related to the desired dilutedconcentration; and (iv) a series of weight signals from the scale; forcalculating the amounts of concentrated chemical feed and diluentrequired to provide a target amount of diluted chemical of desireddiluted concentration which does not exceed the known capacity of thedilution tank; and for controlling the chemical feed flow controller andthe diluent flow controller based upon the series of weight signals toproduce a produced quantity of diluted chemical, the produced quantityrelated to the target amount of diluted chemical and not exceeding thecapacity of the dilution tank; (b) inputting into the system controller:(i) the value related to the dilution tank capacity; (ii) the valuerelated to the variable, concentrated chemical feed concentration; and(iii) the value related to the desired diluted concentration; (c)calculating in the system controller the amount of concentrated chemicalfeed required to provide a target amount of diluted chemical of desireddiluted concentration which does not exceed the dilution tank capacity;(d) charging to the dilution tank the amount of concentrated chemicalfeed calculated in step (c), the amount charged being controlled by thechemical feed flow controller and the system controller based upon aseries of weight values generated by the scale during the charging andtransmitted to the system controller; (e) calculating in the systemcontroller the amount of diluent required to provide a target amount ofdiluted chemical of desired diluted concentration which does not exceedthe dilution tank capacity; and (f) charging to the dilution tank theamount of diluent calculated in step (e), the amount charged beingcontrolled by the diluent feed flow controller and the system controllerbased upon a series of weight values generated by the scale during thecharging and transmitted to the system controller.
 25. The method ofclaim 24, wherein the volume related to the variable concentratedchemical feed concentration is a value related to the weight of ameasured known volume of concentrated chemical feed.
 26. The method ofclaim 25, wherein the value related to the weight of a measured knownvolume of concentrated chemical feed is generated by the scale.
 27. Themethod of claim 24, additionally comprising feeding diluted chemicalfrom a working tank via a pump to a source of water wherein said systemcontroller receives a valve related to a speed of said pump andcalculates the amounts of concentrated chemical and diluent required toprovide a target amount of diluted chemical of desired dilutedconcentration for operating said pump at an optimum efficiency.
 28. Themethod of claim 24, additionally comprising: a chemical supply tank ofknown capacity having a source of liquid concentrated chemical feed, thechemical supply tank mounted upon a scale, the scale being capable ofgenerating a series of weight signals related to the weight of the tankwhen empty and at various levels of filing; a plurality of level sensorslocated inside the chemical supply tank, the level sensors being capableof generating a series of level signals related to the level of the tankat various levels of filing; and wherein the system controllercalculates and displays an amount of concentrated chemical feed in aweight equivalent.
 29. The method of claims 24-28, wherein the chemicalis sodium hypochlorite and the diluent is water.
 30. A monitoring systemfor a liquid concentrated chemical comprising: a tank of known capacity,the tank mounted upon an electronic scale, the scale being capable ofgenerating a series of weight signals related to the weight of the tankwhen empty and at various levels of filling; a plurality of levelsensors located inside the tank, the level sensors being capable ofgenerating a series of level signals related to the level of the tank atvarious levels of filing; a source of liquid concentrated chemicalhaving a first, but variable, concentrated chemical concentration; and asystem controller: for receiving: (a) a value related to the tankcapacity; (b) a value related to the level of the concentrated chemicalin the tank; (c) a value related to the variable, concentrated chemicalconcentration; (d) a series of weight signals from the scale; forcalculating the weight of concentrated chemical concentration; and forconverting the weight of concentrated chemical concentration into anequivalent weight.
 31. The device of claim 30, wherein the equivalentweight is expressed in “equivalent pounds of pure chemical”.
 32. Thedevice of claim 31, additionally comprising a display on the systemcontroller for displaying said equivalent weight of the concentratedchemical concentration.
 33. A monitoring system for aqueous sodiumhypochlorite comprising: a tank of known capacity for sodiumhypochlorite, the tank mounted upon an electronic scale, the scale beingcapable of generating a series of weight signals related to the weightof the tank when empty and at various levels of filling; a plurality oflevel sensors located inside the tank, the level sensors being capableof generating a series of level signals related to the level of the tankat the various levels of filing; a source of liquid concentrated sodiumhypochlorite having a first, but variable, concentrated sodiumhypochlorite concentration; and a system controller: for receiving: (a)a value related to the tank capacity; (b) a value related to the levelof the concentrated sodium hypochlorite concentration feed in the tank;(c) a value related to the variable, concentrated sodium hypochloriteconcentration; and (d) a series of weight signals from the scale; andfor calculating the weight of concentrated sodium hypochloriteconcentration; and for converting the weight of concentrated sodiumhypochlorite concentration into an equivalent weight, wherein saidequivalent weight is expressed in “equivalent pounds of pure chlorinegas”.
 34. The system of claim 33, additionally comprising a display onthe system controller for displaying said “equivalent pounds of purechlorine gas”.
 35. A method for monitoring a liquid concentratedchemical comprising: (a) obtaining a system comprising: a tank of knowncapacity, the tank mounted upon an electronic scale, the scale beingcapable of generating a series of weight signals related to the weightof the tank when empty and at various levels of filling; a plurality oflevel sensors located inside the tank, the level sensors being capableof generating a series of level signals related to the level of the tankat various levels of filing; a source of liquid concentrated chemicalhaving a first, but variable, concentrated chemical concentration; and asystem controller: for receiving: (i) a value related to the tankcapacity; (ii) a value related to the level of the concentrated chemicalin the tank; (iii) a value related to the variable, concentratedchemical concentration; and (iv) a series of weight signals from thescale; for calculating the weight of concentrated chemicalconcentration; and for converting the weight of concentrated chemicalconcentration into an equivalent weight, wherein the equivalent weightis expressed in “equivalent pounds of concentrated chemicalconcentration”. (b) inputting into the system controller: (i) the valuerelated to the tank capacity; (ii) the value related to the level of theconcentrated chemical in the tank; (iii) the value related to thevariable, concentrated chemical concentration; and (iv) the series ofweight signals from the scale; and (c) calculating in the systemcontroller the weight of concentrated chemical concentration; and (d)converting the weight of concentrated chemical concentration into anequivalent weight, wherein the equivalent weight is expressed in“equivalent pounds of pure chemical”.
 36. A system for adjusting a flowof diluted chemical comprising: a tank of known capacity for preparing achemical in a desired diluted concentration, the tank mounted upon anelectronic scale, the scale being capable of generating a series ofweight signals related to the weight of the tank when empty and atvarious levels of filling; a source of liquid concentrated chemical feedhaving a first, but variable, concentrated chemical concentration; achemical feed flow controller for controlling the flow of concentratedchemical feed to the tank; a source of liquid diluent; a diluent flowcontroller for controlling the flow of diluent to the tank; a pump forfeeding the chemical to a water system from the tank, the pump beingcapable of generating a series of signals related to an amount ofdiluted concentration being fed to the water system; and a systemcontroller: (a) for receiving: (i) a value related to the tank capacity;(ii) a value related to the variable, concentrated chemicalconcentration; (iii) a value related to the desired dilutedconcentration; (iv) a series of weight signals from the scale; and (v) aseries of signals from the pump; (b) for calculating the amount ofdiluted concentration being fed to the water system and a pump speed;(c) for calculating the amounts of concentrated chemical feed anddiluent required to provide a target amount of diluted chemical ofdesired diluted concentration which does not exceed the known capacityof the tank wherein said pump speed is within a defined range; and (d)for controlling the chemical feed flow controller and the diluent flowcontroller based upon the series of weight signals to produce a producedquantity of diluted chemical, the produced quantity related to thetarget amount of diluted chemical and not exceeding the capacity of thetank.
 37. A method for adjusting a flow of diluted chemical comprising:a tank of known capacity for preparing a chemical in a desired dilutedconcentration, the tank mounted upon an electronic scale, the scalebeing capable of generating a series of weight signals related to theweight of the tank when empty and at various levels of filling; a sourceof liquid concentrated chemical feed having a first, but variable,concentrated chemical concentration; a chemical feed flow controller forcontrolling the flow of concentrated chemical feed to the tank; a sourceof liquid diluent; a diluent flow controller for controlling the flow ofdiluent to the tank; a pump for feeding the chemical to a water systemfrom the tank, the pump being capable of generating a series of signalsrelated to an amount of diluted concentration being fed to the watersystem; and a system controller: (a) for receiving: (i) a value relatedto the tank capacity; (ii) a value related to the variable, concentratedchemical concentration; (iii) a value related to the desired dilutedconcentration; (iv) a series of weight signals from the scale; and (v) aseries of signals from the pump; (b) for calculating the amount ofdiluted concentration being fed to the water system and a pump speed;(c) for calculating the amounts of concentrated chemical feed anddiluent required to provide a target amount of diluted chemical ofdesired diluted concentration which does not exceed the known capacityof the tank wherein said pump speed is within a defined range; and (d)for controlling the chemical feed flow controller and the diluent flowcontroller based upon the series of weight signals to produce a producedquantity of diluted chemical, the produced quantity related to thetarget amount of diluted chemical and not exceeding the capacity of thetank.